P0455: Evaporative Emission System Large Leak
P0455 is like P0442 but points to a large EVAP leak — often an open/missing fuel cap or a disconnected hose, and it is easier to find than a small leak.
Symptoms
Usually just a check engine light, sometimes a clearer fuel smell than P0442. No performance effect.
Causes
A missing or not-fully-tight fuel cap (most likely), a disconnected/broken EVAP hose, or a purge valve stuck open.
The fix
Confirm the cap is tight first, then visually inspect the large EVAP hoses. Clear the code via OBD2 after the fix and watch for a return.
FAQ
Difference between P0455 and P0442?
P0455 is a large leak (easier to find), P0442 a small one. Both are EVAP and start at the cap.
Does it affect fuel use?
The effect on consumption is tiny, but it raises emissions and keeps the light on.